I used to study with a painter who would appoint one of us (in the workshop) as keeper of the pose. When the model would drift, settle, or get off pose, the "keeper" would correct the pose. He also used to put a dab of masking tape on the wall, or somewhere the model could see it and use it a bit like radar . . . something to fix a gaze on. This usually worked well for everyone.

As to seeing bllue, or any other color on your model, I used to work with another painter who often said that he had never seen a model that affected the background, but he had seen many backgrounds that affected the model . . . in other words, it intirely possible to see blue, or other colors on your model's skin. I'm not sure you should paint it in a garish manner, but it it's there, it ought to be included in some way.